The need to prevent re-use of syringes is widely recognized. One type of single-use syringe effectively destroys the barrel of the syringe through the use of tapered projections carried by the plunger which engage the walls of the syringe. Attempted withdrawal of the plunger from the syringe after an injection causes the tapered projections to puncture the walls. Another type of single-use syringe allows the needle to be retracted into the barrel for disposal. For example, see U.S. Pat. No. 4,507,117 to Vining, et al., dated Mar. 26, 1985 and U.S. Pat. No. 4,826,489 to Haber, et al., dated May 2, 1989.
One of the drawbacks of conventional single-use safety syringes is that they require the user to actively do something to make them safe. In some circumstances, such as when the syringe is being used by drug addicts, proper disposal procedures may not be used. This can result in inadvertent needle sticks by an unsuspecting person who happens to come in contact with the used syringe.